Femoral inserts used in hip joint prosthesis have a polished spherical head mounted on a stem, which is inserted into the intermedullary canal in the femoral bone. Such inserts are advantageously cemented within the canal to hold them fast against the applied forces and loads. Some of them have utilized cement-holding depressions or cavities, such as those shown in the sides of the hip stem shown in drawing sheet No. 2 of U.S. Pat. No. 3,694,820. Such stems with depressions are not as strong as might be desired and are difficult to remove from the canal within the femoral bone if they must be replaced. An object of this invention is to provide a relatively strong hip stem prosthesis for insertion in the intermedullary canal of a femur which can be rigidly installed and which facilitates removal and replacement.